1. Field of the Invention
This invention relates to destructible locking devices of the type employed to releasably interconnect mating components of security devices. Such security devices are widely employed by public utilities to secure meters, supply valves, etc. against unauthorized access.
2. Description of the Prior Art
The operating mechanism of a conventional utility meter is typically enclosed within a transparent dome which in turn is removably attached to the cover of a box-shaped housing. The cover and dome have circular rims that are held in an axially aligned abutting relationship by a channel-shaped split retaining ring. The ends of the retaining ring are configured as mating components which are releasably interconnected in a confronting relationship by locks of varying design.
One such lock of the destructible type is disclosed in U.S. Pat. No. 5,161,838 (Ely et al.), where the mating end components of the split retaining ring are captured between an enlarged head at one end of a stud, and a cap-shaped housing secured to the opposite end of the stud. The stud is further provided with a frangible section adjacent its head which is designed to shear under a compressive load. The load is axially applied by a tool engaging both the cap shaped housing and the head of the stud.
One drawback with this type of lock is that it may be destructively disassembled by any tool capable of exerting the required compressive force. Thus, where multiple utility systems employ locks of this type, one systems"" tools can be used to compromise the security of the other systems"" meters.
A lock of this type also requires a relatively high level of compressive force to shear the frangible stud section. This in turn requires utility personnel to carry tools that are heavy, cumbersome, and have unduly long operating cycles, typically involving the use of wrenches or the like to operate screw actuated force exerting mechanisms.
A general objective of the present invention is the provision of an improved destructible locking device which either obviates or at least significantly minimizes the above described drawbacks of the prior art.
A specific objective of the present invention is the provision of a locking device which is uniquely configured to be destructively disassembled only by a tool having a mating uniquely configured design.
A companion objective of the present invention is the provision of a locking device which may be destructively disassembled by the application of only a relatively modest torque.
The locking device of the present invention is useful, for example, in releasably interlocking two confronting components having aligned openings, typically the ends of a split ring used to secure the transparent dome of a utility meter to the cover of a meter box. In one embodiment to be described hereinafter in greater detail, the locking device includes a hollow cap and a pin having an enlarged head at one end and a nose at its opposite end. The pin is configured and dimensioned to extend through the aligned openings of the confronting components, with its nose received in permanent interlocked engagement in the cap, thereby securely capturing the confronting components between the cap and the enlarged head of the pin. The nose has a frangible portion which may be severed by twisting the nose relative to the pin head. The locking device may be destructibly disassembled by subjecting the pin to a torque sufficient to shear the frangible nose portion. A specially configured tool is engageable with mating specially configured pin segments to effect the required torque application.